Does Eating More Organic Foods Cut the Risk of Cancer?

Association seen for post-menopausal breast and blood cancers

MedpageToday

by Pam Harrison, Contributing Writer, MedPage Today
October 22, 2018

Frequent consumption of organic foods was associated with a significantly lower risk of cancer among French adults versus adults who never consumed organic foods, according to a population-based, prospective study.

In a sample of 68,946 volunteers, self reporting a high organic food score indicative of frequent consumption of organic food (quartile 4 or Q4) was associated with a 25% lower risk of cancer compared with the lowest frequency of organic food consumption (Q1), reported Julia Baudry, PhD, University of Paris, and colleagues.

However, the inverse association between frequent consumption of organic food and cancer risk was confined to postmenopausal breast cancer and all lymphomas including non-Hodgkin's lymphoma (NHL), they noted inJAMA Internal Medicine.

"Organic food standards do not allow the use of synthetic fertilizers, pesticides, and genetically modified organisms and restrict the use of veterinary medications," the investigators stated. "As a result, organic products are less likely to contain pesticide residues than conventional foods. We observed reduced risks for specific cancer sites (postmenopausal breast cancer, NHL ... and all lymphomas) among individuals with a higher frequency of organic food consumption."

Study Details

The NutriNet-Santé study is an ongoing web-based in which investigators are studying the association between nutrition and health. Two months after enrollment, volunteers were asked to provide information on their consumption frequency of 16 labeled organic products, including fruits, vegetables, dairy products, meat and fish, grains, ready-to-eat meals, coffee, tea, chocolate, sugar, and dietary supplements.

"Volunteers were asked to provide information on their consumption frequency of organic products and they could answer, 'I consume these foods most of the time, occasionally, or never'," Baudry explained in an audio interview that accompanied the study. "And for these 16 foods, we summed up the answers and provided an organic food consumption score after which we examined the association between these organic scores and cancer risk." The organic food score ranged from zero to 32 points.

The mean follow-up of the sample was 4.56 years during which researchers identified 1,340 cases of cancer. The most prevalent was breast cancer (34.3%), prostate cancer (13.4%), melanoma and spinocellular carcinoma (10.1%), colorectal cancer (7.4%), NHLs (3.5%), and other lymphomas (1.1%).

After adjusting for confounders, the authors reported that high organic food scores were linearly and negatively associated with the overall risk of cancer (HR for Q4 versus Q1, 0.75, 95% CI 0.63-0.88, P=0.001 for trend).

However, looking at specific sites, "we found that the negative association was the case for all lymphomas, as well as for postmenopausal breast cancer, but we did not find any association with any other cancer sites," Baudry stated. For example, compared to Q1, participants in the highest quartile of organic food consumption (Q4) had a 34% lower risk of postmenopausal breast cancer at a HR of 0.66 (95% CI 0.45-0.96, P=0.03).

For NHL, those in the highest quartile of organic food consumption had a 86% lower risk of developing this particular lymphoma at a HR of 0.14 (95% CI 0.03-0.66, P=0.049) while for all lymphomas, those in the highest quartile of organic food consumption had a 76% lower risk of developing any type of lymphoma at a HR of 0.24 (95% CI 0.09-0.66, P=0.02) compared to those in the lowest quartile.

Investigators also carried out a sensitivity analysis by including the main determinants of pesticide exposure -- namely vegetable products -- in the organic food score. They "did not find any association for postmenopausal breast cancer but we did find that the association remained for all lymphomas," Baudry said.

The findings were no longer statistically significant when researchers analyzed findings by different subgroups, such as younger adults, men, those with only a high school diploma and with no family history of cancer, never and current smokers, and participants who consumed a high quality diet overall.

"Promoting organic food consumption in the general population could be a promising preventive strategy against cancer," the authors concluded. However, they acknowledged that the high cost of organic food remains a significant barrier to more widespread consumption.

Confusion, Conventional Veggies

In an accompanying editorial, Frank B. Hu, MD, PhD, and Jorge E. Chavarro, MD, ScD, both of Harvard T.H. Chan School of Public Health in Boston, and colleagues said the study had several strengths, such as its large sample size, prospective design, and modest loss to follow-up.

In an audio interview, Chavarro noted that one of the most compelling aspects of the study was study consistency with others' reported findings. For example, in the Million Women Study in the U.K., self-reported organic food intake was associated with a 21% lower risk of NHL.

But the editorialists also pointed out some study weaknesses, most notably "the fact that the organic food questionnaire was not validated; therefore, it is unclear what the intended exposure, organic food consumption, was actually measuring. Organic food intake is notoriously difficult to assess, and its self-report is highly susceptible to confounding by positive health behaviors and socioeconomic factors."

Chavarro also noted that food labeling, particularly in the U.S., can be confusing for consumers.

"For example, foods may be labeled 'USDA organic certified,' 'organic,' 'natural,' 'made with organic ingredients,' 'no drugs or hormones used,' or 'sustainably harvested,' so often times people may think they are consuming organic products when they are not," he told MedPage Today in an email.

While all organic foods have less contamination with pesticides and other chemicals than conventionally grown foods, "the benefit in terms of reducing exposure is not the same for all foods," Chavarro added. For instance, differences in pesticide residue contamination between organic and conventionally grown apples or spinach is much greater than the difference between conventionally grown cantaloupes or avocados because people don't eat the peels or skins of products that are exposed to the pesticide itself, so even conventionally grown produce will have relatively low levels of contamination to begin with.

"Therefore, choosing organic versus non-organic foods will not necessarily capture actual exposure to pesticides, and other chemicals, without knowing the specific foods chosen as organic or conventional," Chavarro stated.

Despite these limitations, "I think the main take-away from this study is that we should probably be paying more attention to this issue than we are," he said.

Chavarro's group suggested that for overall health, the benefits of consuming conventionally grown produce likely outweigh the risks of potential pesticide contamination. Indeed, "concerns over pesticide risks should not discourage intake of conventional fruits and vegetables, especially because organic produce is often expensive and inaccessible to many populations," they stated.

The NutriNet-Santé study is supported by the French Ministry of Health, French Institute for Health Surveillance, National Institute for Prevention and Health Education, National Institute for Health and Medical Research, National Institute for Agricultural Research, National Conservatory of Arts and Crafts, and Paris 13 University.

Baudry disclosed support from the Agence Nationale de la Recherche.

Chavarro disclosed support from the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Environmental Health Sciences. Hu disclosed support from the NIH and the California Walnut Commission.

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